Compositions for spray bleaching cellulosic fabrics

ABSTRACT

A composition is provided for spray bleaching cellulosic fabrics. The composition comprises a wetter, hydrogen peroxide, a caustic, a stabilizer, an optical brightener, and water. When the composition is sprayed onto the surfaces of the cellulosic fabric, it achieves penetration into the fabric so that a uniform whiteness is achieved throughout the fabric.

FIELD OF THE INVENTION

The invention relates generally to the bleaching of cellulosic greige fabrics, and, more particularly, to compositions that may be sprayed for uniformly bleaching both surfaces of a fabric.

BACKGROUND OF THE INVENTION

Today, fabrics are made from a wide-variety of natural fibers, such as cotton, synthetic fibers, and combinations thereof. The basic fabric is a greige fabric that must be dyed, or bleached in order to provide the desired whiteness and brightness to the resultant fabric and/or garment.

There are numerous known methods for bleaching fabrics, including the use of continuous ranges and high temperature jets. Continuous range bleaching involves a multiple step process, including the application of an optical brightener to make the fabric look whiter following a fabric rinse and nip step. In some cases, this requires re-handling of the fabric, which adds to process time. The fabric must be handled again as it is moved to a pad machine for the application of a softener that imparts hand to the fabric, and then to a dryer. In high temperature jet bleaching, the bleaching chemicals are applied at higher temperatures than are obtained in a continuous range, and optical brighteners are exhausted onto the fabric. In this process, however, the size of the load of fabric in the jet vessel is limited, therefore increasing the time and labor required to load and unload smaller quantities of fabric. The fabric must then be moved to the pad machines for application of a softener. Thereafter, the fabric must be moved to the dryers.

In the dyeing arts, one of the more cost effective methods of dyeing a fabric is spray dyeing. Spray dyeing, as used herein, includes conventional spraying as well as atomization and electrostatic application. It has now been found that spray bleaching is also possible, applying the same principles. A problem with spray bleaching that has been encountered, however, has been to provide uniform bleaching on both sides of the fabric. To attempt to achieve such uniformity requires spraying both sides of the fabric or garment in a very controlled environment. Also, the fabric or garment must remain in a taut position in order to provide a flat and even distribution of the bleach formulation onto the fabric or garment, yet not have any area that is covered or unavailable for receipt of the spray.

What is needed, therefore, is a composition for bleaching cellulosic, especially greige, fabrics that provides uniform scouring and/or bleaching on both sides of the fabric. It is particularly important to provide such a composition that can bleach cotton to the desired whiteness in one basic spray step or operation without the need for a controlled environment and without the problems noted above for positioning the fabric or garment, yet with good bleach penetration into the fabric or garment.

The above-described and other advantages and features of the present disclosure will be appreciated and understood by those skilled in the art from the following detailed description and appended claims.

DETAILED DESCRIPTION

Certain exemplary embodiments of the present invention are described below. The embodiments described are only for purposes of illustrating the present invention and should not be interpreted as limiting the scope of the invention, which, of course, is limited only by the claims below. Other embodiments of the invention, and certain modifications and improvements of the described embodiments, will occur to those skilled in the art, and all such alternate embodiments, modifications and improvements are within the scope of the present invention.

The present invention is directed to formulations for bleaching cellulosic fabric. More particularly, the present invention relates to compositions for uniformly providing, preferably by spraying, a bleach formulation on both surfaces or sides of a cotton fabric. In one embodiment, the composition comprises a wetter, hydrogen peroxide, a caustic, a stabilizer, an optical brightener, and water.

The wetter of the present compositions facilitates movement of the other constituents of the composition, particularly the hydrogen peroxide, i.e., the bleaching agent, into the fabric. The wetter is a blend of one or more surfactants, and, more particularly, a nonionic compound of surfactants that provides detergent cleansing properties and creates hydrophilicity in the fabric. One commercially available wetter is ULTRAVON® CN-US, available from Huntsman International LLC, in Salt Lake City, Utah.

The wetter comprises an amount between about 32 grams per liter (g/l) and about 64 g/l of the composition. In one embodiment, the wetter comprises about 40 g/l.

As is well known in the art, hydrogen peroxide has strong oxidizing properties and is, therefore, an effective bleaching agent. The hydrogen peroxide is present in an amount of between about 80 g/l and 150 g/l. The amount of hydrogen peroxide is dependent upon the makeup of the greige fabric to be bleached. For example, some fabrics contain numerous cotton seeds, organic contaminants, relatively insoluble knitting oils, and minerals such as magnesium and calcium from the soil in which the cotton is grown. Certain fabrics also require cleaner and brighter fabric bases. The base whitening of the hydrogen peroxide, along with the alkali (caustic soda) in the composition, bleach the cotton fiber to a white in preparation for the optical brighteners, which create the fluorescent brightness of white. In the embodiment described herein, the hydrogen peroxide comprises about 100 g/l.

The caustic (50 percent soda) is selected from sodium hydroxide, sodium carbonate, or soda ash. The caustic soda increases the pH of the solution to between about 10.5 and 11.0, which is needed to activate and initiate the whitening action of the hydrogen peroxide. The high pH of the caustic also breaks down any organic compounds and dissolves the cotton seeds. The caustic comprises an amount between about 5 g/l and 90 g/l. In the embodiment described herein, the caustic is sodium hydroxide and comprises about 30 g/l. This amount, however, is dependent upon the initial condition of the fabric being treated.

The stabilizer may be an organophosphorus compound, which is the primary constituent for providing chemical stability to the total composition. A stabilizer is an integral part of the composition due to the volatile oxidation properties of the hydrogen peroxide, which creates heat when mixed with the alkali and water. Since the composition has all of the necessary components to bleach and whiten fabric, the stabilizer also helps to keep the optical brightener from precipitating out of the solution. The organophosphorus compound comprises an amount between about 5 g/l and 50 g/l. In one embodiment, the organophosphorus compound comprises about 20 g/l. One suitable stabilizer is TINOCLARITE® CBB, also commercially available from Ciba Specialty Chemicals in High Point, N.C.

The optical brightener, or optical brightening agent (OBA), is provided to absorb light in the ultraviolet and violet regions (usually 340-370 nm) of the electromagnetic spectrum. The optical brightener may be a distyryl biphenyl compound comprising an amount between about 0.1 g/l and 1.0 g/l. In the embodiments described herein, the optical brightener comprises about 0.2 g/l. One suitable optical brightener is UNITEX® NFW, also commercially available from Ciba Specialty Chemicals in High Point, N.C. This optical brightener should be able to withstand the high pH conditions of the composition described herein, as high pH conditions are detrimental to some optical brighteners.

Optionally, and depending upon the quality of the water supply, a chelator, which is a softener, may be added to the composition. The chelator is used to remove hard metals from the water, and prevents precipitation that leads to unevenness in the whiteness of the fabric. It may also assist in stabilizing the composition. Thus, a chelator may not be needed in the composition if minerals, such as hard metals, are not present in the fabric itself or in the water source. Chelators that may be used in the present composition include, but are not limited to, a blend of amino acid derivatives or pentasodium salt of diethlentriaminepenta acetic acid. If needed, the chelator comprises an amount between about 1 g/l and 20 g/l.

Also, optionally, an alkali, such as sodium silicate, may be added to the composition, depending upon the quality of the greige fabric, to further assist in bleaching the fabric. If needed, the sodium silicate comprises an amount between about 10 g/l and 90 g/l. Sodium silicate also may be used in the composition as a stabilizer for the oxidation of the hydrogen peroxide and caustic soda.

Turning next to the method of applying the composition of the present invention, all of the ingredients are mixed simultaneously, preferably in an in-line, spray head. For example, each ingredient is transported to a sleeve or manifold having a mixer, such as a corkscrew therein, to mix together all of the constituents of the composition before they enter the spray head.

Following mixing, the composition is sprayed on the surfaces or sides of a fabric using one or more spray nozzles. The manifold and spray nozzles may be fixed in position as the fabric is moved beneath or above them. Alternatively, the spray nozzles may be movable with respect to each surface or side of the fabric so that a substantially even coat of the composition is applied to the surfaces of fabric. One method of spray dyeing, which also has applicability to spray bleaching, is disclosed in U.S. Pat. No. 7,033,403, which is incorporated herein by reference.

Advantageously, the composition may be applied by spraying onto the two surfaces or sides of the fabric in between about one and twenty seconds, and optimally between about five seconds and twenty seconds. The time is dependent upon the amount of saturation needed to penetrate the fibers. This saturation is measured in terms of wet pickup calculations. The percentage of wet pickup is dependent upon the saturation and absorption of the fabric. Wet pickup is calculated after the composite solution is sprayed onto the fabric and a wet piece of the fabric is weighed. The piece is then rinsed with continuously running water, removing all of the sprayed composition. The fabric piece is then dried and weighed again. The weight of the sprayed piece minus the dry weight, divided by the weight of the sprayed fabric, yields the wet pickup. A wet pickup of between about 60 percent and 90 percent has been found to be optimal.

It should be recognized that the present invention contemplates any number of spray nozzles and numerous nozzle orientations. Also, the size of the head of a spray nozzle may vary.

Thus, the present compositions, which avoid the use of a controlled environment and provide an ability to bleach all cellulosic fabrics, particularly greige, facilitates manufacturing flexibility in that rapid changeovers from a bleach composition to a dye formulation on the same spray application machine are possible.

Another benefit achieved by the use of the present compositions to spray bleach cellulosic fabrics is that one can effectively and efficiently bleach long continuous runs of fabric with the compositions described herein, significantly reducing the time and labor required by known bleaching methods.

The invention has been described herein in terms of several embodiments and constructions that are considered by the inventor to represent the best mode of carrying out the invention. It will be understood by those skilled in the art that various modifications, variations, changes and additions can be made to the illustrated embodiments without departing from the spirit and scope of the invention. These and other modifications are possible and within the scope of the invention as set forth in the claims. 

1. A composition for spray bleaching cellulosic fabrics, comprising: (a) a wetter; (b) hydrogen peroxide; (c) a caustic; (d) a stabilizer; (e) an optical brightener; and (f) water.
 2. The composition of claim 1, wherein the wetter comprises a surfactant.
 3. The composition of claim 2, wherein the surfactant comprises between about 16 g/l and 32 g/l of the composition.
 4. The composition of claim 1 wherein the hydrogen peroxide comprises between about 20 g/l and 250 g/l of the composition.
 5. The composition of claim 1, wherein the caustic is sodium hydroxide.
 6. The composition of claim 5, wherein sodium hydroxide comprises between about 10 g/l and 150 g/l of the composition.
 7. The composition of claim 1, wherein the stabilizer is an organophosphorus compound.
 8. The composition of claim 7, wherein the organophosphorus compound comprises between about 5 g/l and 50 g/l of the composition.
 9. The composition of claim 1, wherein the optical brightener is a distyryl biphenyl compound.
 10. The composition of claim 9, wherein the distyryl biphenyl compound comprises between about 1 g/l and 20 g/l of the composition.
 11. The composition of claim 1, further comprising a chelator.
 12. The composition of claim 11, wherein the chelator is a softener.
 13. The composition of claim 1, further comprising a silicate.
 14. The composition of claim 13, wherein the silicate is sodium silicate.
 15. The composition of claim 14, wherein the sodium silicate comprises between about 10 g/l and 90 g/l of the composition.
 16. A composition for spray bleaching cellulosic fabrics, comprising: (a) a wetter comprising between about 16 g/l and 32 g/l; (b) hydrogen peroxide comprising between about 20 g/l and 250 g/l; (c) a caustic comprising between about 10 g/l and 150 g/l; (d) a stabilizer comprising 5 g/l and 50 g/l; (e) an optical brightener comprising between about 1 g/l and 20 g/l; and (f) water. 